1. Field of the Invention
The present disclosure generally relates to image forming and, more particularly, to image forming apparatuses such as a laser beam printer (LBP), a digital copier, and a digital facsimile (FAX) which perform optical writing by using laser beams.
2. Description of the Related Art
In an electrophotographic type image forming apparatus, a laser beam emitted from a laser light source is reflected by a rotating polygon mirror so that the laser beam modulated through an image signal scans a surface of a photosensitive member. In many image forming apparatuses, the polygon mirror is being stopped while a user does not provide an instruction for a print operation, and a scanner motor that rotates the polygon mirror starts being driven upon the user instructing the print operation to be started.
Japanese Patent Laid-Open No. 2001-96799 discusses the following method. That is, after a scanner motor is started, an image forming apparatus stands by for a predetermined period of time in which it is estimated that the number of rotations of a rotatable polygon mirror converges at the number of rotations that allows exposure to be performed (i.e., that allows an image to be formed on a recording material) after the number of rotations of the rotatable polygon mirror has reached a predetermined number of rotations. Then, the determination of a scanner ready state (i.e., the number of rotations of the rotatable polygon mirror has reached a level that allows an image to be formed on a recording material) is made. Here, the estimated predetermined period of time is selected on the basis of the time it takes for the cycle of rotations to reach a predetermined value.
However, in the method discussed in Japanese Patent Laid-Open No. 2001-96799, the predetermined period of time in which it is estimated that the number of rotations of the rotatable polygon mirror reaches the level that allows exposure to be performed needs to be set to a period of time with some margins while taking an error arising due to a variation in an operating environment or a component into consideration. In addition, the image forming apparatus always stands by for the predetermined period of time after the number of rotations of the rotatable polygon mirror has reached the predetermined value. Thus, there may be a case in which a timing at which the determination of an exposure ready state is unnecessarily delayed by continuing to stand by for the predetermined period of time while the number of rotations of the rotatable polygon mirror has actually converged at the level that allows exposure to be performed. In such a case, there may be a case in which a timing at which an image starts to be formed on a recording material is unnecessarily delayed as well. As a result, a first print output time (FPOT), which is the time it takes for an image to finish being formed on a first piece of the recording material after an instruction for the image to start being formed is received, may be unnecessarily extended, and the user may need to wait for the extended period of time.